Impregnation of polyfilamentous sutures with synthetic polymer particles

ABSTRACT

Polyfilamentous sutures having the attributes of a monofilamentous suture are prepared by impregnating the sutures with an aqueous dispersion of inert, synthetic polymeric particles and then subjecting the impregnated suture to centrifugal force to simultaneously extract water and dry the suture.

United States Patent urtz [54] IMPREGNATION OF POLYFILAMENTOUS SUTURESWITH SYNTHETIC POLYMER PARTICLES [21] Appl. No.: 732,859

[52] [1.5. CI. ..128/335.5,ll7/l01', 117/141,

117/161 R [51] Int. Cl. ..A6lI17/00 [58] Field ofSearch ..l17/l01, 141,145, 161 R, 169; 128/3355 1 1 *May 36, 1972 [56] References Cited UNITEDSTATES PATENTS 2,888,363 5/1959 Matter et al. .1 17/102 x 3,322,1255/1967 Kurtz ..128/335.5 2,193,188 3/1940 Bradley... 1 28/3355 2,478,2298/ 1949 Be ..260/29.6 2,734,506 2/1956 Nichols et a]. 128/3355 2,890,1366/1959 Vaughan et a1 ....117/143 3,379,552 4/1968 Kurtz ..117/73,424,164 1/1969 BlOCh et al ..128/335.5

Primary Examiner-Edward G. Whitby Attorney-Larson, Taylor & Hinds [57]ABSTRACT Polyfilamentous sutures having the attributes of amonofilamentous suture are prepared by impregnating the sutures with anaqueous dispersion of inert, synthetic polymeric particles and thensubjecting the impregnated suture to centrifugal force to simultaneouslyextract water and dry the suture.

6 Claims, No Drawings IMPREGNATION OF POLYFILAMENTOUS SUTURES WITH STICPOLYMER PARTICLES This invention relates to surgical sutures. Moreparticularly, the invention relates to sutures having decreasedreactivity with tissue and to a method for their preparation.

Sutures are classified either as absorbable or nonabsorbable and may bepolyfilamentous or monofilamentous. Polyfilament sutures are preferredby surgeons because they have superior knotting characteristics relativeto monofilament materials; On the other hand, monofilament sutures arepreferable for the patient as there is less trouble in cases ofinfection.

It is generally accepted that monofilaments, such as monofilamentstainless steel, monofilament nylon, monofilament polyethylene andmonofilament polypropylene are the most inert of the nonabsorbablesutures. When implanted in an area where infection occurs, as a rule,they are not spit" spontaneously by the wound, nor do they requiresurgical removal. On cross section, all of these monofilaments have onething in common. They are solid with no dead spaces or interstices.

On the other hand, braided and twisted sutures when implanted whereinfection occurs, will, as a rule, be spit spontaneously by the wound,or require surgical removal in order for healing to occur. On crosssection, the braided and twisted sutures consist of many filaments anddead spaces. For example, on cross section, braided silk has 40 to 50percent dead space.

On the basis of the above facts, it seems possible that there is adirect relationship between dead spaces in a suture and the incidence ofspontaneous spitting or the necessity for surgical removal of the suturewhen infection occurs. if this hypothesis is correct, monofilamentsshould be the sutures of choice for the patient undergoing surgery.However, surgeons have a great deal of difiiculty in their use. All ofthem are stiff, difficult to knot, and have a tendency to openspontaneously. Some, in addition, have sharp ends, kink, or are tooelastic. All monofilaments apparently pose difficulties in surgicaltechniques. Many surgeons continue to use the monofilaments despitetheir problems because of the excellent patient response. However,obviously, monofilaments cannot be used if the surgical knottingtechnique becomes inadequate.

It is an object of the present invention to provide a method wherebypolyfilament sutures can be imbued with monofilament characteristics.

These and other objects, which will become apparent in light of thedescription which includes a preferred embodiment, are achievedaccording to the invention by substantially eliminating the dead airspaces in a polyfilamentous suture by filling the interstices of thesilk suture with a plurality of solid particles of synthetic polymericmaterials. It has been discovered that the reactivity of thepolyfilamentous suture can be reduced to such an extent that reactivityof the suture is as low as reactivity of a monofilament when these solidparticles are incorporated therein.

The inert material used to fill the sutures may be any suitable inert,insoluble, synthetic polymeric material small enough to penetrate theinterstices of the silk suture. Tetrafluroethylene polymers such asTeflon(polytetrafluoroethylene) are particularly suitable as particles.Other inert, insoluble synthetic resins which can be used includepolyolefins such as polyethylene, polypropylene and the like;polydiolefins such as polymers of butadiene and isoprene; polystyrene;polyesters, polyamides and like materials. Aqueous dispersions of thesematerials such as the aqueous dispersions of Teflon described in Berry,US. Pat. No. 2,478,229 are suitable to incorporate the particles intothe suture. Saturated aqueous dispersions are particularly suitable.Ordinarily, the inert particles employed will have a particle size of upto 1 micron.

The sutures which can be improved according to this invention includeall nonabsorbable sutures. Illustrative of such sutures are polyfilamentsutures made from silk; hydrophobic synthetic materials such aspolyesters (e.g. Dacron), polyolefins (e.g. polypropylene), polyamides(e.g. nylon and polyacrylonitrile), and like materials;- cotton andlinen.

It is believed that by filling the dead space within the interstices ofthe silk suture, the pockets which are conducive to harboring invadingorganisms are eliminated or at least reduced to an extent that clinicalresults indicate that the su ture is monofilamentous. In other words,while it is not certain that the voids are eliminated, the suturesproduced in accordance with this invention behave like a monofilament.In any event, the amount of the particles introduced into the sutureshould be an amount sufiicient to render the suture substantiallymonofilamenteous. It is preferred, however, that the particlessubstantially fill the dead space within the interstices of the suture.The exact amount of particles necessary to fill the dead spaces withinthe suture varies with the nature and configuration of the suture and,of course, on the density of the particulate matter employed. Forinstance, a minimum of about 6 percent by weight ofpolytetrafluoroethylene based on the weight of the suture up to as muchas may be impregnated into the suture and which will remain there isgenerally used to render the suture substantially monofilamentous. Themaximum will depend upon techniques as well as materials and pressurizedimpregnations that may be used. it should be noted, however, that asuture exhibiting monofilamentous characteristics can be obtainedwithout entirely filling the dead spaces in the suture.

Impregnation of the suture is accomplished in accordance with thepresent invention by immersing the suture in an aqueous dispersion ofthe solid polymeric particles for a time sufficient to introduce saidpolymeric particles into the suture. After the immersion, theimpregnated suture is subjected to centrifugal force to extract thewater carrier and simultaneously dry the suture. This extraction-dryingstep has been found to provide a suture having the polymeric particlesdistributed and set uniformly and homogeneously throughout the entiresuture. Thus, the method of the invention prevents the dripping andexuding of the aqueous dispersions from the impregnated suture whichcauses nonuniform distribution and loss of impregnated particulatematter.

Any suitable centrifuge or spinning means capable of providing acentrifugal force sufficient to remove the water carrier and dry thesuture while spinning can be used. It is preferred, however, that arelatively slow extractor be employed in order to avoid the throwing offof impregnated solid particles that is likely to occur with excessivelyfast extractors. Although fast extractors, for example, extractorshaving a spinning rate of 1600 to 1750 or more r.p.m., can be employedfor the extraction-drying operation, they frequently necessitaterepeated impregnation-spinning cycles to provide the desired finalproduct. Use of slower extractors for the extraction-spinning operationsuch as an extractor having a spinning rate of about 700 r.p.m., forexample, provides the desired impregnated suture in a single cycle. Thespin time will vary, of course, with the centrifugal force to which theimpregnated suture is subject. With the slower extractors, the spin timeis usually at least 1 minute. If desired, heat may be provided thespinning means to reduce the spinning time.

Wax, of course, has been used for treating polyfilament silk sutures foryears. Likewise, silicones have also been proposed to treat Dacron andsilk polyfilament sutures for various reasons. In these and allanalogous instances, however, the sutures when used clinically havebehaved like polyfilaments and not like monofilaments. If is believedthat the monofilament characteristics achieved by the present inventionare due primarily to the use of dispersions of the solid particles toload the suture with the particulate matter. The old wax-type andsilicone treatments have been strictly concerned with the use of liquidsolutions of the was or silicon material.

The following examples are included to further illustrate the presentinvention.

EXAMPLE I A silk suture is immersed in a suspension of colloidal sizeTeflon (polytetrafluoroethylene) particles available from Dupont asTeflon Te 3170, and having an average particle size of about 0.2 micron.The suspension described by Berry, US. Pat. No. 2,478,229 is alsosuitable for this purpose. The suture has a core of 3 ends of 2 threadsand a braided cover of 12 ends of 2 threads. The total denier of thesuture is 420. The impregnation is continued for 5 minutes after whichit is subjected to spinning and drying for minutes in a spin-extractorat a spinning rate of 700 r.p.m. The resulting suture exhibits a weightgain of about 9 percent and behaves substantially like a monofilament.The particles of Teflon remain tenaciously imbedded in the body of thesuture and repeated wash cycles will not dislodge a detectable amountthereof.

The sutures can be sterilized in the usual manner and at any stage ofmanufacture or may be sterilized by the user. Since silk sutures tend toswell in water or steam, it is preferred to sterilize them byelectromagnetic radiation techniques or with ethylene oxide. The suturesmay, of course, be attached to surgical needles.

EXAMPLES lI-lll Polyfilamentous silk sutures exhibiting monofilamentcharacteristics can be prepared by substituting the following syntheticparticles in the process described in Example I: Examplell-polyethylene; Example III-polystyrene in latex EXAMPLE IV A 40polyfilamentous suture made from Dupont type 55 Dacron and having a 4thread core of 56 denier and a braided cover with two threads of 13-15denier per carrier is provided with monofilamentous characteristics byimpregnating the suture by the method described in Example 1 above.

It is claimed:

1. A method for imparting attributes of a monofilament to a polyfilamentsuture comprising the steps of immersing a polyfilamentary suture in anaqueous dispersion of insoluble, inert synthetic polymeric particles,the particles being of a size sufficiently small to enter within theinterstices of the suture, maintaining the immersion to introduce saidpolymeric particles into said suture in an amount sufficient to imbuethe polyfilament suture with substantially monofilamentous propertiesand subjecting said impregnated suture to centrifugal force tosimultaneously extract water and dry said suture.

2. A method according to claim 1 wherein the suture is polyfilament silkand the synthetic polymeric particles are particles oftetrafluoroethylene polymer.

3. A method according to claim 2 wherein the tetrafluoroethyleneparticles are polytetrafluoroethylene particles having an average sizeof up to 1 micron.

4. A method according to claim 3 wherein the suture is filled with atleast 6 percent by weight said particles based on the weight of thesuture.

5. A suture comprising a polyfilamentary silk suture having a pluralityof fine, solid particles of inert, insoluble, synthetic polymericmaterial incorporated in the interstices thereof in an amount sufiicientto imbue the polyfilament silk suture with substantially the propertiesof a monofilament.

6. The suture of claim 5 wherein the solid particles are oftetrafluoroethylene polymer.

2. A method according to claim 1 wherein the suture is polyfilament silkand the synthetic polymeric particles are particles oftetrafluoroethylene polymer.
 3. A method according to claim 2 whereinthe tetrafluoroethylene particles are polytetrafluoroethylene particleshaving an average size of up to 1 micron.
 4. A method according to claim3 wherein the suture is filled with at least 6 percent by weight saidparticles based on the weight of the suture.
 5. A suture comprising apolyfilamentary silk suture having a plurality of fine, solid particlesof inert, insoluble, synthetic polymeric material incorporated in theinterstices thereof in an amount sufficient to imbue the polyfilamentsilk suture with substantially the properties of a monofilament.
 6. Thesuture of claim 5 wherein the solid particles are of tetrafluoroethylenepolymer.